Boxer countered that Fiorina has based her political run on her corporate resume, so the matter was fair game.
"She's running on her record as the former CEO of Hewlett-Packard. What she did there counts, so I'm going to keep on telling the truth about it," Boxer said.
The candidates also sparred over immigration. Fiorina reiterated her objections to comprehensive immigration reform. But in a nod to the importance of Latino voters, who make up 18% of the state's likely voters, Fiorina said for the first time Wednesday night that she would support the so-called DREAM Act, which would allow certain undocumented youths to earn legal status by attending college or serving in the military.
It was a rare moment of agreement: Boxer is a co-sponsor of that bill.
During the debate, sponsored by the San Francisco Chronicle, KQED-FM and KTVU television, the candidates offered their views on a host of issues, including:
• Global warming: Fiorina did not directly answer when asked whether she believes global warming is real. "We should always have the courage to examine the science," she said, "but all scientists agree on this: The only way to impact global warming is to act globally. A state acting alone will make no difference."
She criticized Boxer's efforts to pass federal legislation that would have cut greenhouse gas emissions through a program of emission permits. Boxer's bill, Fiorina said, "was completely the wrong track" and would have cost "trillions of dollars in lost economic output [and] millions of jobs."
But Fiorina declined to take a position on Proposition 23, the November ballot measure that would suspend California's landmark global warming law until unemployment drops to 5.5% or lower for four consecutive quarters.
Boxer seized on her opponent's reticence, using it as an excuse to return to Fiorina's record at HP:
"If you can't take a stand on Prop. 23 I don't know what you will take a stand on," Boxer said. "If we overturn California's clean energy policies that's going to mean that China takes the lead away from us with solar, that Germany takes the lead away from us with wind, but I guess my opponent is kind of used to creating jobs in China and other places. I want those jobs created here in America."
• Same-sex marriage: Fiorina again said she opposes same-sex marriage, and supports civil unions and the repeal of "Don't Ask, Don't Tell." But she declined to answer when asked if the federal government should recognize civil unions for purposes such as Social Security benefits.
Boxer, who also favors the repeal of the strictures against gays and lesbians in the military, said homosexual couples would gain full equality only when same-sex marriage was recognized. "The only way to get the rights that married couples have is to go for marriage equality," she said. "I'm glad to say I believe people are coming around to see it."
• Assault weapons ban: Fiorina restated her opposition to the federal assault weapons ban, saying the law is vague and ineffective. "We have loads of laws, and most of the time, criminals are breaking those laws and we are curtailing citizens' lawful rights to carry guns," she said. "The assault weapons ban is extremely arbitrary about what qualifies as an assault weapon."
Boxer countered that such bans have kept people safe. "To go back to that dangerous yesterday makes no sense at all," she said. "It has bipartisan support."
• Stem-cell research: Fiorina said she felt comfortable allowing federal funding to go to research using adult stem cells, as well as embryos that would have been destroyed otherwise. "It is when embryos are produced for the purposes of destruction, for the purposes of stem cell research that I have a great deal of difficulty," she said. Boxer did not address the question, which was directed to Fiorina.